3,051 research outputs found

    Simple Combined Model for Nonlinear Excitations in DNA

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    We propose a new simple model for DNA denaturation bases on the pendulum model of Englander\cite{A1} and the microscopic model of Peyrard {\it et al.},\cite{A3} so called "combined model". The main parameters of our model are: the coupling constant kk along each strand, the mean stretching y∗y^\ast of the hydrogen bonds, the ratio of the damping constant and driven force γ/F\gamma/F. We show that both the length LL of unpaired bases and the velocity vv of kinks depend on not only the coupling constant kk but also the temperature TT. Our results are in good agreement with previous works.Comment: 6 pages, 10 figures, submitted to Phys. Rev.

    Effect of Disorder in the Frustrated Ising FCC Antiferromagnet: Phase Diagram and Stretched Exponential Relaxation

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    We study the phase transition in a face-centered-cubic antiferromagnet with Ising spins as a function of the concentration pp of ferromagnetic bonds randomly introduced into the system. Such a model describes the spin-glass phase at strong bond disorder. Using the standard Monte Carlo simulation and the powerful Wang-Landau flat-histogram method, we carry out in this work intensive simulations over the whole range of pp. We show that the first-order transition disappears with a tiny amount of ferromagnetic bonds, namely p∼0.01p\sim 0.01, in agreement with theories and simulations on other 3D models. The antiferromagnetic long-range order is also destroyed with a very small pp (≃5\simeq 5%). With increasing pp, the system changes into a spin glass and then to a ferromagnetic phase when p>0.65p>0.65. The phase diagram in the space (Tc,pT_c,p) shows an asymmetry, unlike the case of the ±J\pm J Ising spin glass on the simple cubic lattice. We calculate the relaxation time around the spin-glass transition temperature and we show that the spin autocorrelation follows a stretched exponential relaxation law where the factor bb is equal to ≃1/3\simeq 1/3 at the transition as suggested by the percolation-based theory. This value is in agreement with experiments performed on various spin glasses and with Monte Carlo simulations on different SG models

    Integrated power passives

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    A multi-layer film-stack and method for forming the multilayer film-stack is given where a series of alternating layers of conducting and dielectric materials are deposited such that the conducting layers can be selectively addressed. The use of the method to form integratable high capacitance density capacitors and complete the formation of an integrated power system-on-a-chip device including transistors, conductors, inductors, and capacitors is also given

    The Current Adoption of Dry-Direct Seeding Rice (DDSR) in Thailand and Lessons Learned for Mekong River Delta of Vietnam

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    The paper documents the joint study trip, organized by CCAFS Southeast Asia for Vietnamese rice researchers, extension workers, as well as local decision makers, to visit Thailand in April 2018. The goal of the study trip was to observe and learn the experience of Thai farmers on the large-scale adoption process of dry-direct seeding rice (DDSR), a viable alternative to address regional scarcity of fresh water in irrigation caused by the drought and salinity intrusion in the Mekong River Delta

    A new flyback DC-to-three-phase converter with sinusoidal outputs

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    Systematic extension of any dc-to-dc converter leads to its dc-to-three-phase equivalent characterized by sinusoidal output voltages and fast dynamic responses. This genralization principle is illustrated for the special case of the flyback topology. State-space averaging has modeled with a high degree of accuracy the performance of dc-to-dc converters. Here it is combined with the stationary-to-rotating coordinate transformation, customarily used in polyphase ac systems, to results in an effective analysis method for switched-mode dc-to-polyphase converters

    A deep level set method for image segmentation

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    This paper proposes a novel image segmentation approachthat integrates fully convolutional networks (FCNs) with a level setmodel. Compared with a FCN, the integrated method can incorporatesmoothing and prior information to achieve an accurate segmentation.Furthermore, different than using the level set model as a post-processingtool, we integrate it into the training phase to fine-tune the FCN. Thisallows the use of unlabeled data during training in a semi-supervisedsetting. Using two types of medical imaging data (liver CT and left ven-tricle MRI data), we show that the integrated method achieves goodperformance even when little training data is available, outperformingthe FCN or the level set model alone

    Frustration Effects in Antiferromagnetic FCC Heisenberg Films

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    We study the effects of frustration in an antiferromagnetic film of FCC lattice with Heisenberg spin model including an Ising-like anisotropy. Monte Carlo (MC) simulations have been used to study thermodynamic properties of the film. We show that the presence of the surface reduces the ground state (GS) degeneracy found in the bulk. The GS is shown to depend on the surface in-plane interaction JsJ_s with a critical value at which ordering of type I coexists with ordering of type II. Near this value a reentrant phase is found. Various physical quantities such as layer magnetizations and layer susceptibilities are shown and discussed. The nature of the phase transition is also studied by histogram technique. We have also used the Green's function (GF) method for the quantum counterpart model. The results at low-TT show interesting effects of quantum fluctuations. Results obtained by the GF method at high TT are compared to those of MC simulations. A good agreement is observed.Comment: 11 pages, 19 figures, submitted to J. Phys.: Condensed Matte
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